fix: Update port and protocol handling for GENEVE in aws_lb_listener

[DanielRis]

Description

aws_lb_listener now drop port and protocol when the resolved listener protocol is GENEVE, matching Gateway Load Balancer expectations.

Motivation and Context

• Previous behaviour forced explicit values for port/protocol, which fails for GWLB listeners that must omit them.

│ Error: creating ELBv2 Listener (arn:aws:elasticloadbalancing:us-east-1:111111111111111:loadbalancer/gwy/my-gwlb-LGwJla8P/0ac3a7b141f63121): operation error Elastic Load Balancing v2: CreateListener, https response error StatusCode: 400, RequestID: 5b0cfb9b-e361-4826-971e-241a73712909, api error ValidationError: A protocol cannot be specified for gateway listeners
│ 
│   with module.example.module.loadbalancer.aws_lb_listener.this["geneve"],
│   on .terraform/modules/example.loadbalancer/terraform-aws-alb-10.3.0/main.tf line 116, in resource "aws_lb_listener" "this":
│  116: resource "aws_lb_listener" "this" {
│ 

│ Error: creating ELBv2 Listener (arn:aws:elasticloadbalancing:us-east-1:111111111111111:loadbalancer/gwy/my-gwlb-LGwJla8P/0ac3a7b141f63121): operation error Elastic Load Balancing v2: CreateListener, https response error StatusCode: 400, RequestID: 792e8f9e-2c83-461f-91ba-678d6db8eedf, api error ValidationError: A port cannot be specified for gateway listeners
│ 
│   with module.example.module.loadbalancer.aws_lb_listener.this["geneve"],
│   on .terraform/modules/example.loadbalancer/terraform-aws-alb-10.3.0/main.tf line 116, in resource "aws_lb_listener" "this":
│  116: resource "aws_lb_listener" "this" {

Setting it null resulted into

│ Error: Error in function call
│ 
│   on .terraform/modules/example.loadbalancer/terraform-aws-alb-10.3.0/main.tf line 276, in resource "aws_lb_listener" "this":
│  276:   port                                                                  = coalesce(each.value.port, var.default_port)
│     ├────────────────
│     │ while calling coalesce(vals...)
│     │ each.value.port is null
│     │ var.default_port is null
│ 
│ Call to function "coalesce" failed: no non-null, non-empty-string arguments.

Breaking Changes

• None; non-GENEVE listeners behave exactly as before.

How Has This Been Tested?

• Successful ALB/NLB deployment with/without the fix
• Successful ALB/NLB drift detection with/without the fix (no changes) to ensure no breaking changes
• Successful GWLB deployment with the fixed TF module

[antonbabenko]

Applied identical coding style.

[antonbabenko]

This PR is included in version 10.3.1 🎉